The present invention relates to systems for automatically detecting and extinguishing flue fires by completely mechanical means.
Many homeowners have added wood stoves or fireplaces to their homes to supplement their primary heating source or even to be the main source of heat. These systems incorporate flue pipes to exhaust combustion gases and by-products to the atmosphere. As the stove is used, unburned materials such as wood tar build up on the interior of these flue pipes. This is especially so when green wood is burned or the fire is dampened down in moderate weather. If these unburned materials are not cleaned out frequently and are allowed to build up, they may easily be ignited, creating a fire in the flue which may readily spread to the rest of the house.
Both manual and automatic devices and systems have been invented to combat flue fires. Manual systems require that an operator be aware of the fire and be available to activate the system. But when a wood stove is used to heat a house, there may not always be someone available to watch the stove. Further, some of these require excessive time and in some cases extra equipment. For example, U.S. Pat. No. 4,393,941 to Stevens requires the operator to mount a ladder against the house so that he can drop a garden hose, which is attached to an outdoor spigot, down the chimney.
Automatic systems fall into two catagories: electrically operated and mechanically operated. The electrically operated systems obviously require a source of electricity which may not be available at the time of the fire. The wires running to the system may have been destroyed by spreading fire, the electricity in the house may have been knocked out by fire, or the loss of electricity may be the reason the wood burning stove is being used in the first place. If the electricity went out before the fire, that may be the reason why the fire in the stove has been stoked up sufficiently to cause the flue fire as well. If a battery pack were used at the source of electricity, the owner would have to periodically replace or recharge the batteries so that the system remains operational.
Mechanical systems tend to use fusible links and/or tend to be located on the roof of the house. Both types are difficult to reset. Fusible links must be resoldered with the appropriate solder or replaced and reattached so that the system is once again operational. This is even more difficult when the system is located within the upper part of the chimney. Further, systems that are located in the roof or in the upper part of the chimney are subject to the extremes of weather which may affect their ability to operate. Significantly, in roof based systems the fire extinguishing material is far away from the source of the fire. The bottom or base of the flue pipe is where combustion by-products accumulate and where the flue fire is most likely to occur. The by-products accumulate near the bottom of the flue due to the expansion and contraction of the flue during use which causes the particles to flake off and fall to the bottom of the flue. In a roof based system, the updraft within the flue, quite strong during a flue fire, may carry the extinguishing material out of the chimney before it has a chance to reach the fire.